1. Field of the Invention
The present invention relates to a method for the manufacture of an electronic device which has at least a transparent conductive layer, such as a semiconductor photoelectric conversion device, field effect transistor, liquid crystal display or the like, and more particularly to improvement in an electronic device manufacturing method which includes at least a step of forming a transparent conductive layer member and a step of patterning the transparent conductive layer member by one or more laser beams into the transparent conductive layer.
2. Description of the Prior Art
Heretofore there has been proposed an electronic device manufacturing method which includes at least a step of forming a transparent conductive layer member and a step of patterning the transparent conductive layer member by means of a laser beam to form a transparent conductive layer. Compared with another manufacturing method which employs a photolithography technique for the formation of such a layer, the abovesaid method excels in that the transparent conductive layer can be formed without any defects. The reason for this is that in the case of forming the transparent conductive layer by photolithography, a photoresist mask therefor is prone to pinholing or exfoliation at its marginal edges, which results in the formation of defects, whereas the method utilizing the patterning process using a laser beam has no such factors which cause defects.
With the conventional method employing the patterning technique for the formation of the transparent conductive layer through use of a laser beam, it is a general practice to use a YAG laser which emits a laser beam having a relatively long wavelength of about 1060 nm.
The absorption coefficient of the abovesaid the transparent conductive layer member for the laser beam of such a relatively long wavelength is extremely small. For example, when the transparent conductive layer member consists principally of a sublimable metallic oxide such as SnO.sub.2, In.sub.2 O.sub.3 or ITO (Indium-Tin Oxide), its absorption coefficient is 10.sup.2 /cm or less. The reason for this is as follows: In the case where the laser beam has a wavelength as large as 1060 nm, its optical energy is smaller than the optical energy band gap of the transparent conductive layer member. For instance, in the case of the laser beam having the wavelength of 1060 nm, its optical energy is about 1.23 eV. On the other hand, when the transparent conductive layer member consists principally of such a sublimable metallic oxide as SnO.sub.2, In.sub.2 O.sub.3 or ITO, its optical energy band gap is in the range of 3 to 4 eV.
For the patterning of the transparent conductive layer member by the laser beam, it is necessary that the beam be high-powered, since the absorption coefficient of the transparent conductive layer member for the laser beam: is extremely small. When the transparent conductive layer member is as thin as 2 .mu.m or less, it is feared that a substrate and other layers underlying it is damaged or patterned. Also it is feared that the marginal edges of the transparent conductive layer are swollen or exfoliated.
Furthermore, in the case of the laser beam having such a relatively long wavelength of 1060 nm or so, it is difficult to reduce its minimum spot diameter to a small value of 100 .mu.m or less. Therefore, it is difficult, with the conventional manufacturing method, to finely form the transparent conductive layer with high precision. In addition, in the case of simultaneously forming a plurality of transparent conductive layers, they cannot be spaced apart a small distance of 100 .mu.m or less. This imposes severe limitations on the fabrication of a small and compact electronic device having the transparent conductive layer.